Misconceptions on the Impact of Climate Change in Sunderbans

Gautam Kumar Das

Sea-level rise and subsidence in the Sunderbans due to climate change accelerate two important processes that lead to the sediment loss – i) denudation or erosion and ii) submergence or inundation. Denudation or erosion is the result of physical washing of sediment by the tidal current and wave action, while submergence or inundation is the regular submergence of low-lying zone depending upon topographic set up or geomorphic situation of the coastal areas of the estuarine Sunderbans. Apart from the sea-level rise, there are several factors like accretion through siltation, presence of floral assemblage, supply of sediments etc that cause and consider the net sediment budget in the estuarine Sunderbans. Collection of data through scientific survey and analyses on sediment budget, preparation of scientific simulation models in this area of morphodynamics pattern are required for interpretation of the causes of such process of sedimentation and inundation, and prediction of the projected sea-level rise due to climate change in the Sunderbans.

The global sea-level, in an average has been rising at the rate of 1.0 – 2.5 mm/year for the last 100 years, where the Sunderbans is not beyond an exception from that of the sea-level rise. Further, the prediction of sea-level rise for the ensuing 100 years, stipulated by the climate change, would be in an average range from 20 to 86 cm/year as computed and recorded in the IPCC (Intergovernmental Panel on Climate Change) Second Assessment Report. Sunderbans is not out of such climate change, sea-level rise, subsidence and its impact. As a result, Sunderbans faces vulnerability which is the degree of incapability to cope with the consequences of climate change, subsidence and sea-level rise.

Climate change is not only a vast concept, but its impact is covered with the entire region of the Sunderbans inclusive its surrounding areas. Sunderbans too face the impact of climate change by means of subsidence and sea-level rise and it is quite natural. Sunderbans remain devoted to that climate change through fair and foul, though the ultimate arbiter is the nature. Yet, people in majority off and on, fall in misconceptions on the impact of climate change in the Sunderbans. Sometimes they blame all the adverse effects as a result of climate change and accelerated sea-level rise thereon due to the incapability to cope with the situations faced in the Sunderbans. Undoubtedly, major changes are the results of the climate change, but a few changes are exceptional, these are seemed to be the misconceptions on the impact of climate change, as evidenced in the Sunderbans. A complete destruction of a bivalve bed in the coastal areas of Fraserganj might be considered as an instance to be claimed as one of such misconceptions.

An enriched bed of Glauconome sculpta (Sowerby), a typical pelecypod or bivalve under the phylum Mollusca is in existence for 30 years in the intertidal zone of Fraserganj of the coastal Sunderbans. Of late that pelecypod bed has gradually been vanishing as this zone is inundated maximum period except only period of lowest low tide during full moon and new moon. The intertidal zone of Fraserganj gradually becomes lowland as a consequence of huge physical removal of sediments due to erosion and that’s why the area is inundated with the tidal sea water almost rejecting the concept of inundation or submergence of water due to sea-level rise as a result of climate change.

The coastal managers generally prescribe for alltime nourishing beaches instead of constructing sea wall, or introducing a building set back apart from allowing construction next to the coastline. There is neither sea wall nor an embankment constructed to restrict the water intruded during flood tidal current or wave action. This is how Fraserganj, a coastal zone of natural phenomenon, faces loss of such an important biotic community for almost permanent inundation as a consequence of sediment loss or erosion which might be a misconceptualism thought of the process of sea-level rise due to climate change.

Remains of tree trunks in different depths from the surface layer are noticed from the excavated ponds from four spots of Debnagar under Namkhana P.S., Paschim Sripatinagar under Patharpratima P.S., Jharkhali under Basanti P.S. and Khas Kumarkhali under Canning P.S. in and around the areas of the Sunderbans having maximum distance of about 100 km in between Debnagar and Khas Kumarkhali and minimum distance of about 30 km in between Debnagar and Paschim Sripatinagar. The availability of the remains of tree trunks in different depths in all four excavated ponds ranging from 1 m to 3 m in the 100 km2 area might infer the process of subsidence for the specimens collected at Debnagar and Khas Kumarkhali of Port Canning area, and the relics of remaining tree trunks might be occurred in the lowland areas like creek or on the river flood plain that are silted up gradually which is a natural phenomenon in the lower deltaic plain and as a result of such sedimentation the above mentioned depositional areas become parallel to the surface layer with time, though the entire lower Gangetic plain stands in the subsiding zone geologically. Subsidence at a vast area never happens to be occurred in the different depths particularly in the Sunderbans region. It is evidenced from the occurrence of in-depth tree trunks that the entire region of the Sunderbans has gradually been subsiding because of the gradual maturity and attaining steadiness of the lower deltaic plain of the Bengal Basin.

Apart from erosion, huge accretion through siltation results burial of pneumatophores that lead to degeneration and destruction of mangroves. There is no trace of salt marsh or other wetland grasses in the entire portion of the crescentic point bar like region adjacent to Masnad – e – Aala of Hijli area, Purba Medinipur district. Area of Hijli stood at the opposite side of the Sagar Island around the confluence of Hugli River and the Bay of Bengal, is never considered in the mapping of the Sunderbans, though it is covered with the mangroves and the nature of this area is as good as the Sunderbans. Here destruction of mangroves as because of the huge sedimentation process might reject the fact of inundation as a consequence of sea-level rise due to climate change. Thus off and on a few events or evidence misconceive the actual meaning or significance on the impact of climate change particularly in the Sunderbans that leads to misconceptualism.

Jan 16, 2019

Gautam Kumar Das [email protected]

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